It appears that Marcus Overhagen, a well-known BeOS developer, has been recieving threats from YellowTAB. Marcus writes: "Using an alleged NDA (non disclosure agreement) breach, he promises to undertake everything that is possible to sue me. He claimes that even this mail is protected by the NDA that I signed with Yellowtab, but I'm certain that it doesn't apply here. At the end, he says that a copy of that mail was sent to their lawyer, who is now checking legal measures against me."

I am only aware of one active Haiku contributor that is working for yT, but I don't understand how that can be translated into "yT supports Haiku", at least not beyond allowing this developer to work on Haiku in his spare time.
We (as Haiku) are not competing with yellowTab, nor are we fighting each other. They can benefit from our code, and we're allowing them to do so. I think they donated some copies of Zeta to Haiku developers, though, but that's as far as "supporting" goes currently.
I also wondered about this "without yT Haiku wouldn't be where it is today" - AFAICT we would be at the exact same stage without them as we are today. The time they actively participate in Haiku development has yet to come, if ever.